[SI-LIST] Re: SSO pushout, ground bounce definition

From: Alex McPheeters <amcpheeters@xxxxxxxx>
To: francis.kai@xxxxxxxxx,"'mark.gailus@xxxxxxxxxxxx'" <mark.gailus@xxxxxxxxxxxx>
Date: Thu, 25 Apr 2002 14:51:34 -0400
Actually, this whole exchange has been fascinating and informative.

Alex


At 11:14 AM 4/25/02 -0700, Kai, Francis wrote:
>
>Mark,
>
>     I agree with you that "ground bounce" is a misleading terminology
>because it implies that the "ground" is "bouncing", which is not the case. I
>only say that it is tough to find an appropriate term to describe it, even
>"simultaneous switching noise" may not be a term that fully describes this
>physical phenomenon.
>     When I was an Assistant Professor at Northeastern University many years
>ago, I happened to know
>Prof. Lance Glacer of MIT. He was teaching the VLSI course and I had to
>learn from him (using his book) to teach an advance VLSI course at
>Northeastern. I told him that "VLSI" was very tough. He replied, "Of course,
>it is a multi-billion dollar business." Prof. Glacer measured the level of
>difficulty based on the dollar in business. I believe the "signal integrity"
>is getting tougher and tougher because it has pulled more money into it.
>       For the "electromotive force" term, you can say that you are right
>because in engineering applications we can always use a definition in a much
>broader sense. Usually engineers are not scientists and they do not care
>much about definitions and scientific concepts. What engineers do care is
>whether they can design a working product and sell it to make a profit. I
>came from a family of Liberal Arts and I was trained to use words correctly
>and properly (in the Chinese language) when I was a boy. For example, I
>don't like the term "high tech" but it generates a lot of money and it also
>supports my family. So I live with it. "High tech" translates into "Gao Ke
>Zi" in Chinese and in fact it should have been translated into "Gao ji ke
>Zi." Nobody uses the term "Gao ji ke Zi."
>      I hope we do not bore the whole si-list subscribers.
>
>Best regards,
>
>Francis
>   
>
>-----Original Message-----
>From: mark.gailus@xxxxxxxxxxxx [mailto:mark.gailus@xxxxxxxxxxxx]
>Sent: Thursday, April 25, 2002 9:50 AM
>To: Kai, Francis
>Cc: 'mark.gailus@xxxxxxxxxxxx'; Kai, Francis; si-list@xxxxxxxxxxxxx;
>tom_pitten@xxxxxxxxxxxxxxxxxx; phil_stokoe@xxxxxxxxxxxxxxxxxx
>Subject: RE: [SI-LIST] Re: SSO pushout, ground bounce definition
>
>
>
>Hello, Francis.
>
>1) I agree completely with your words:
>
>"The "high-speed ground" has new meaning embedded in it."
>
>That is an excellent statement and I like your background discussion
>leading up to it.
>
>2) I see that I cannot convince you that "ground bounce" is misleading
>terminology and should not be used, so I will not try any further on that
>topic. :-)
>
>3) As far as the use of the term "electromotive force" (EMF) goes, I think
>that you are correct in pointing out that the original and most correct
>meaning of this term is for the voltage produced accross a chemical cell or
>battery.  However, there exists a widespread electrical engineering usage
>of the term EMF to include also the voltages induced by changing magnetic
>fields, or induced on conductors which are moving through a magnetic field.
>Shadowitz is more precise in distinguishing betweeen EMFs and voltages.  He
>writes (page 385 of "The Electromagnetic Field", Dover 1988):
>
>"The nonconservative electric field Eind ( "E induced" ) induced in one
>part of a circuit by some means is not usually the primary object of
>interest; that role is played by (equation: Vba=the line integral of Eind
>from point a to point b) a quantity called the induced voltage.  MOST
>PEOPLE CALL THIS QUANTITY THE ELECTROMOTIVE FORCE, OR THE EMF, BUT WE WILL
>USE THE TERM VOLTAGE EXCLUSIVELY."
>
>(Emphasis mine -- mg)
>
>This whole discussion may seem like nit-picking to some, but "circuit" (as
>opposed to "field") engineers would benefit from more precise terminology
>that matches if possible the established terminology of physics.
>
>Regards,  Mark Gailus
>
>
>
>
>
>
>
>
>"Kai, Francis" <francis.kai@xxxxxxxxx> on 04/23/2002 07:42:38 PM
>
>To:   "'mark.gailus@xxxxxxxxxxxx'" <mark.gailus@xxxxxxxxxxxx>, "Kai,
>      Francis" <francis.kai@xxxxxxxxx>
>cc:   si-list@xxxxxxxxxxxxx, tom_pitten@xxxxxxxxxxxxxxxxxx,
>      phil_stokoe@xxxxxxxxxxxxxxxxxx
>
>Subject:  RE: [SI-LIST] Re: SSO pushout, ground bounce definition
>
>
>Dear Gurus and Mark,
>
>     I read Mark's new message and the only thing I agree with him is that
>there are not enough English words to describe the modern technology today.
>(English majors: where are you?) Since there are not enough English words,
>a term is used for different concepts can cause confusion and misleading
>in science and technology.
>
>     When I was a student in National Taiwan University, our teacher in
>the Electromagnetic Wave course, Chen Tsun-hsiung, told us that there are
>two different concepts in Electromagnetic theory, i.e., the "field concept"
>and the "circuit concept." Later I found them out in the book,
>"Time-Harmonic
>Electromagnetic Fields," by R.F. Harrington. The "circuit folks" care about
>the "grounds," and the "field folks" normally don't care about "grounds."
>In
>the
>famous book, "Field Theory of Guided Waves," by Robert E. Collin, the term
>"ground" is not even in the subject index! Collin belongs to the "field
>folks."
>Therefore Mark pointed out that "there is wisdom in the microwave
>engineers'
>
>dictum that 'there is no such thing as ground'," which is based on the
>"field folks"
>concept.
>
>     A ground is originally defined as an equipotential point or plane that
>serves
>as a reference potential for a circuit or system. The "equipotential"
>concept
>is originated in electrostatics, where charge is involved. Unfortunately,
>in
>
>modern high-speed digital circuit when coupling is involved, such
>"electostatic equipotential" no longer exists in this system. Therefore we
>use
>the term, "ground," is no longer identical to the original term "ground"
>developed long time ago in electrostatics. The "high-speed ground" has new
>meaning embedded in it.
>
>     The "electromotive force," or emf, concept derives from the line
>integral of
>an electric field, Ee, generated by the chemical action in the battery.
>(I have the book by Albert Shadowitz but it is not in my office now.)
>Therefore it has nothing to do with the "ground bounce" concept discussed
>here.
>I do not think it is appropriate to use the term "electromagnetic force
>caused by
>changing currents in these same conductors," or "common-mode effects may
>produce
>roughly the same electromotive force along all power, ground, etc.," since
>it was
>not originally defined in this way.
>
>    The "ground bounce" effect is a relatively new but important concept in
>high-speed
>digital circuitry. Before our English majors find a new term for this
>concept, I
>believe we shall still use it.
>
>Regards,
>
>Francis
>
>
>
>
>
>
>
>-----Original Message-----
>From: mark.gailus@xxxxxxxxxxxx [mailto:mark.gailus@xxxxxxxxxxxx]
>Sent: Tuesday, April 23, 2002 11:24 AM
>To: francis.kai@xxxxxxxxx
>Cc: si-list@xxxxxxxxxxxxx; tom_pitten@xxxxxxxxxxxxxxxxxx;
>phil_stokoe@xxxxxxxxxxxxxxxxxx
>Subject: [SI-LIST] Re: SSO pushout, ground bounce definition
>
>
>
>(Sorry: my previous message was missing its last few lines.  --mg)
>
>Dear Francis,
>
>(1) I agree with your criticism of the use of the term "fluctuation" for
>this phenomenon.  It does have special meanings in other areas of physics,
>and for that reason should not be used in this case.  However, I still
>agree with Raymond Chen that "ground bounce" is a misleading and, I think,
>even a nonsensical term.  Perhaps "power/ground noise", "power/ground
>transients", or even "power/ground bounce" would be an improvement.  "SSO",
>etc, are also OK with me.  What do other SI-Listers have to say? The
>crucial point here, I feel, is that it is not an effect that is determined
>by the configuration of "ground" conductors or ground currents alone, but
>by the interaction of ground conductors with signal and power conductors
>and currents, etc.
>
>(2) With regard to uniqueness of voltages, you have encouraged me to
>clarify my thoughts -- thank you -- that is always a good thing -- and I
>agree that my terminology was imprecise.
>
>Let's see if I can be any clearer today:
>
>I agree that in an actual physical circuit, Electric and Magnetic Fields
>and Fluxes (as well as charges and currents) are uniquely determined.
>
>Where I think there are pitfalls, is in the "mapping" of a transient
>electromagnetic problem such as SSO, into the more restricted types of
>descriptions allowed by circuit theory.
>
>In electromagnetics we can separate an arbitrary electric field into
>conservative (i.e, curl free) and purely nonconservative components, and
>speak of the path integral of one as "potential difference" and the other
>as "voltage" or "electromotive force".
>
>(Typically, this electromotive force might involve something like a
>chemical battery, or something like a conductor placed in a region with a
>changing magnetic field, such as  the secondary of a transformer, or the
>various pins of a device package, connector, etc.  There is an nice short
>discussion of "voltage" or "electromotive force" versus "potential
>difference" at the start of Chapter 11-1 on Faraday's Law, in  the book
>"The Electromagnetic Field", by Albert Shadowitz, Dover Publications. )
>
>It is a common practice to model the set of conductive pins in a device
>package or a connector as coupled inductors.  Up to some frequency, a set
>of coupled inductors includes the effects of electromotive forces caused by
>changing currents in these same inductors, and if expanded into a lumped or
>distributed multiconductor transmission line model includes the effects of
>electromagnetic waves travelling "along" the intended transmission
>direction.  However, by itself, neither model includes the effects of
>electromotive forces in these same conductors associated with radiating
>fields from the whole set of conductors, or with "externally" incident
>fields on the outside of the set of conductors, or in other words, "common
>mode" effects. This omission can give rise to differences of certain
>predictions of these circuit theory models versus the real system.
>Accuracy of agreement depends upon whether these differences are important
>to the particular results being sought in the simulation. These common mode
>effects, by definition, may produce roughly the same electromotive force
>along all power, ground, and signal conductors in the "length" of the
>interconnection, and therefore substantially "cancel out" in calculation of
>"voltage differences" between various conductors at one or the other end of
>the interconnections.
>
>The result is that of the various voltages measureable in the simulation
>circuit, some accurately match the real world, and some do not.  As you
>said, it is a separate problem to determine which "voltages" we can
>measure.  Even here, I think, the ones we can most easily measure are
>exactly those which are more "automatically" in agreement between the
>circuit model and the real world.
>
>(You can tell -- I am still thinking.)
>
>Thanks and best egards,
>
>Mark Gailus
>
>
>
>
>"Kai, Francis" <francis.kai@xxxxxxxxx>@freelists.org on 04/19/2002 06:20:20
>PM
>
>Please respond to francis.kai@xxxxxxxxx
>
>Sent by:  si-list-bounce@xxxxxxxxxxxxx
>
>
>To:   "'mark.gailus@xxxxxxxxxxxx'" <mark.gailus@xxxxxxxxxxxx>,
>      chen@xxxxxxxxxxx
>cc:   si-list@xxxxxxxxxxxxx, "Kai, Francis" <francis.kai@xxxxxxxxx>
>
>Subject:  [SI-LIST] Re: SSO pushout, ground bounce definition
>
>
>
>Dear Gurus,
>
>     I do not agree with Mark on certain concepts listed below, however,
>any
>
>comments are welcome.
>
>(1) "Fluctuation" has a quite different meaning if you agree with the
>concept
>in Statistical Mechanics or Thermodynamics. The "Fluctuation theory"
>phenomena
>do differ from the "ground bounce" effect occurred in signal integrity.
>Therefore, if we want
>to be consistent with physics (or physical concepts), the term
>"Power/ground
>fluctuation" will
>not be as nice as "ground bounce" in signal integrity.
>
>(2) I do not see the term "voltages" is not "uniquely defined". All those
>theorems,
>Ohms Law, Tellegen theorem, Maxwell Equations, do represent that voltages
>are well-defined uniquely in an Electrical System. These theorems satisfy
>the ODE (ordinary differential equations) and PDE (partial differential
>equations)
>and are well-posed. Therefore, "uniqueness" is guaranteed. There is no
>theorem
>to prevent voltages to be measurable, like Heisenberg's Uncertainty
>Principle in
>quantum mechanics. However, whether Mark or any other engineers/technicians
>can
>accurately measure those voltages is a different story.
>
>Best regards,
>
>Francis Kai
>
>-----Original Message-----
>From: mark.gailus@xxxxxxxxxxxx [mailto:mark.gailus@xxxxxxxxxxxx]
>Sent: Friday, April 19, 2002 2:06 PM
>To: chen@xxxxxxxxxxx
>Cc: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: SSO pushout, ground bounce definition
>
>
>
>
>Raymond,
>
>Thanks for a very clear presentation.  I agree with you on all points,
>especially the following:
>
>(1) "Power/ground fluctuation" is a much clearer term than "ground boun=
>ce",
>which is always misleading and should not be used.
>
>(2) In the real world and in EM theory, "voltages" (i.e., differences o=
>f
>electric potential) are frequently not uniquely defined or measurable,
>particularly between "distant" points or where radiation can take place=
>.
>
>(3) With respect to multiconductor transmission lines: "Voltage drop al=
>ong
>the ground conductor (except DC) is not well defined based on EM theory=
>."
>
>I will add a couple of generic observations:
>
>Much confusion and mischief results when inappropriate oversimplified
>circuit-theory models are applied to electromagnetic problems.
>
>There is wisdom in the microwave engineers' dictum that "there is no su=
>ch
>thing as ground".
>
>Best regards,
>
>Mark Gailus
>
>Teradyne
>
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Alex McPheeters
Vice President, Business Development
American Computer Development Inc.
Office - (301) 620-0900
Fax - (301) 620-9099
Cell - (301) 305-3051
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References:
- [SI-LIST] Re: SSO pushout, ground bounce definition
  - From: Kai, Francis
[SI-LIST] Re: SSO pushout, ground bounce definition

Other related posts:
